puzzle of dobbs family in Glasgow

[Courtneyg]

so here is my odd puzzle... not that it really matters in the long run but I'm curious to know why and how.
here is the back story

john dobbs (name on on marriage reg dubbs) married helen bowman 1880 irregular marriage (everything on registry matches perfectly)
1881 census they are living as husband and wife (but under john and Ellen dubbs)
in 1890 she has a son named charles bowman illegitamate (mother Helen bowman)
no sign of john dobbs, dibbs, or dobbs anywhere for the 1890 census expect one crew list for ss city of new york 1890
1891 census helen living with her father and son both named Charles.
in 1901 census we have helen and john dobbs with  the children Charles Dobbs 11  Helen Dobbs 9 John Dobbs 4 William Dobbs 3 (his birth reg is what gave me marriage date and place)
all children birth reg under dubbs lol
oh and as an added interesting note 1911 census she stated to have had 7 living children. and of course married for thirty something years

heres the question that bothering me, why would a married woman go back to maiden name and then have illegitimate child under that name? wouldn't she just keep dobbs/dubbs.... charles ended up taking the dobbs name anyway.
any ideas?
or will this just go into the pile of "we will never know because it was over 100 years ago."
thanks for reading!

[Forfarian]

heres the question that bothering me, why would a married woman go back to maiden name and then have illegitimate child under that name? wouldn't she just keep dobbs/dubbs

If she had a major falling out with her husband, there is no reason why she should keep his name. In Scots Law, a woman doesn't legally lose her own maiden name* when she marries, so dropping the name of an unwanted husband is not a problem. And it's not all that  unusual for deserted wives (and even widows) to have illegitimate children.

In the 1880s and 1890s divorce was difficult and very expensive, so unless there was a strong incentive for a divorce people didn't usually bother.

*You quite often find a married woman in the census, living with her husband, listed as his wife, but using her own name. I found one just the other day in the 1881 census, but it's more common in the earlier censuses.

[Courtneyg]

Ahhhh scots law! Didn't think of googling that one.
Occam's razor at its finest lol
I'll learn so much my asking the small questions
Thank you for the reply!